Laser imaging a lanographic printing plate

Abstract

A planographic printing plate which is imaged by means of a laser beam in combination with overall exposure to ultraviolet light and developed by means which are conventional in lithographic art.

What is claimed is: 
     
       1. The method of making an imaged printing plate comprising the steps of: (a) providing a planographic printing plate which comprises, on a substrate, a layer which contains an organic-solvent-soluble negative working diazo compound, carbon particles and a self-oxidating binder;   (b) selectively removing areas of said layer by means of a laser beam so as to define on the plate an image which is sensitive to ultraviolet light;   (c) exposing the plate overall to ultraviolet light; and   (d) developing the plate to cause the image areas struck by laser beam to accept ink and the non-image areas to accept water.   
     
     
       2. The method in accordance with claim 1 wherein the laser beam is provided by a YAG laser.